Module errors

Error types for stream variants

Enums

• EthHandshakeError
  Error that can occur during the eth sub-protocol handshake.
• EthStreamError
  Errors when sending/receiving messages
• P2PHandshakeError
  Errors when conducting a p2p handshake.
• P2PStreamError
  Errors when sending/receiving p2p messages. These should result in kicking the peer.
• PingerError
  An error that can occur when interacting with a pinger.